Process for production of alkyl phenols of improved color



'tion or surface active agents.

United fi trates Fatent @hhcc 3,,ld85ih t ster-tired Fol o, 2, 1965 This invention relates to a method of producing alkyl phenols of improved color. More specifically the invention relates to a process of inhibiting the formation of color in the productin of alkyl phenols.

Alkyl phenols are widely used in the paper, textile, dye and other industries as intermediates in the prepara- Alkyl phenols are generally produced by reacting phenol with an alltylation agent, i.e. olefin, in the presence of an acidic alkylation catalyst, such as boron trifluoride, sulfuric acid, hydrogen chloride, ferric chloride, aluminum chloride, and the like. The alkyl phenols thus produced are'usually condensed with lower alltylene oxides in the presence of a basic condensing catalyst such as potassium hydroxide. These condensates are usually used as surfactants and are known as nonionic surface active agents. When many alkyl phenols, specifically octyl and nonyl phenols are produced by the prior art methods, they are often dark and discolored. What actually is responsible for the discoloration is not certain. There are many theories as to why color is found in alkyl phenols and attempts have been made to determine the nature of the color.

One theory advanced as to why color exists in alkyl phenols is that there are latent color bodies present in the olefins used to prepare the alkyl phenols. Even though the olefins may have been treated to remove visible color bodies, latent color bodies present in these olefins and which are initially colorless, will, on exposure to air, light, heat or other atmosphericinfiuences, markedly discolor the alkyl phenol material.

Still another theory is that color develops even though the starting olefins have been treated to remove color, the color being due to some unknown reaction mechanism which occurs during the alkylation. Thus, What actually is responsible for color in the alkyl phenols is still uncertain and the fact remains that the unwanted color does develop in the final alkyl phenol product, notwithstanding how or why color develops. The problem of eliminating color from the alkyl phenols is a long standing one in the art as indicated above and the conventional treatment to remove such color is to repeatedly Wash and distill the alkylatcd phenol. While this treatment is etrective in most cases, it obviously is time consuming and expensive. Also, in some instances color persists even after such treatment.

US. Patent No. 2,727,928, Menu et al., December 20, 1955, discloses the use of hypophosphorous acid and salts of hypophosphorous acid as color stabilizing agents for alkyl phenols. However, this patent does not relate to the inhibition of the formation of color in alkyl phenols during their preparation. It merely relates to the stabilization against deterioration in color and odor upon storage of an already prepared and decolorized alkyl phenol.

As indicated above, the procedures presently employed to obtain colorless alltyl phenols from discolored materials have been costly, laborious and in some cases, ineffective. Important uses of these products have been as intermediates in the preparation of surface active agents for use in the textile, paper, dye and chemical industries, wherein discoloration must be avoided in order for these products to be usable. Therefore, it

will be appreciated that colorless alkyl phenols are required for industry.

It is therefore, an object of this invention to provide a new and useful method of producing alkyl phenols with improved color.

It is also an object of this invention to provide a new and useful method of inhibiting the formation of color in the production of alkyl phenols.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

It has been discovered that the foregoing objects are eadily accomplished by a process which involves the steps of adding a small amount of a color inhibiting agent such as hypophosphorous acid or one of its derivatives to phenol and thereafter reacting the phenol containing the color inhibiting agent with an alkylating agent in the presence of an allcylation catalyst. We have found that when aikyl phenols are prepared in accordance with the process disclosed in this invention, further purification steps are not required to improve and stabilize the color of the resulting product.

The steps involved in the practice of this invention are straightforward. Phenol, a small amount of hypophosphorous acid or derivative thereof and the alkylation catalyst are brought together and the phenol present in the resulting mixture is then reacted with an alkylation agent. I

The amount of hypophosphorous acid or derivatives thereof necessary for the prevention of color formation in the final alkyl phenol product is usually small. It is usually employed in proportions of approximatey 0.65% to 2.00% based on the total weight of the reactants including the alkylation agent, As illustrative of the pres: ent invention, hypophosphorous acid or derivatives thereof can be added to the phenol in the form of a 50% by weight aqueous solution. Other strengths of hypophosphorous acid or derivatives thereof can also be used, as for example 106% solid hypophosphorous acid. However, for convenience a 50% water solution is used. The preferred amount of hypophosphorous acid. or derivatives thereof used is about 0.15% based on the total weight of'the reactants. However, generally speaking,

the amount of hypophosphorous or derivative thereof to be used will depend somewhat on the amount of coloring material to be removed as well as onthe reaction conditions, and may be varied with satisfactory results. Quantities less than disclosed will produce noticeable improvements in color. Quantities greater than disclosed may be used. However, for reasons of economy it seldom ing there is a progressive breakdown of hypophosphorous acid to phosphoric acid and phosphine. The latter is a malodorous, poisonous and spontaneously flammable gas. The breakdown of the acid is illustrated by the following equation:

zmro -an ro rn in general the alkyl phenols of this invention are produced by mixing phenol, hypophosphorous acid or derivative thereof, and an acid alkylation catalyst, heating the mixture and adding the alkylation agent to the mixture at a rate that will favor the formation of alkyl phenol. The amount of heat and the rate at which the alkylating agent is added to the mixture must be determined experimentally for each .alkylation system. The process of our invention is ideally suitable for preparing alkyl phenols wherein the alkyl group or groups contain from 2 to 20 carbon atoms per group. The alkylation agents that have been found suitable for use are those aliphatic olefins containing from 2 to 20 carbon atoms or mixtures thereof. Exemplary of aliphatic olefins that have been found suitable as alkylation agents are ethylene, propylene, butylene, isobutylene, diisobutylene, vtriisobutylene, octene, nonene, decene, centene, etc. and mixtures thereof. It is obvious that when alkyl halides are used as the alkylating agents to prepare the alkyl phenols, our process will function equally as well.

The ratios of phenol to alkylation agent that may be employed in producing alkyl phenols which can be treated by the process of our invention varies widely, depending on the reaction temperature, amount of alkylation catalyst and the particular alkylation agent used to prepare the alkyl phenol. These ratios may easily be found by experimentation. It is to be understood that our invention is directed to the production of alkyl phenols of improved color by having present certain agents during the alkylation of the phenol and hence is not limited by the conditions of alkylation. Due to the diverse nature of the molar proportions and reaction conditions employed in the preparation of individual alkylated phenols or their mixtures, it is impossible to set forth specific reactions and molar proportions: which will adequately encompass the preparation of alkyl phenols. However, such conditions and proportions can easily be determined by anyone skilled in the art.

The process disclosed in this invention can easily be incorporated into a continuous batch system or a continuous flow system for the production of alkyl phenols.

Upon completion of the alkylation reaction, any excess phenol remaining in the reaction mass can be stripped from the alkylated material by distillation under reduced pressure with or without prior removal of the alkylation catalyst.

Thus it is readily apparent that our novel process provides an economical and efiicient process for inhibiting and preventing the formation of color in the preparation of alkyl phenols. Further, our process employs the equipment normally used in the production of alkyl phenols and does not require the purchase of any new equipment. Our process is one of inhibition or" color in the preparation of alkyl phenols, not a process of subsequently removing color present in existing alkyl phenol as is taught in the prior art. Hence, our process eliminates. the distillation and/ or recrystallization steps employed by the prior art to remove color ordinarily formed during the production of alkyl phenols. Thus our process is a more economical and eflicient one for producing stabilized alkyl phenols than those found in the prior art.

For a fuller understanding of the nature and objects of the invention reference should be had to the following example which is given merely as a further illustration of the invention and is not to be construed in a limiting sense.

4- Example In this example, 0.16 gram of an aqueous solution of hypophosphorous acid (50% concentration) was added to 94 grams (1.0 mole) of phenol in a reaction vessel. 1.6 grams of boron trilluoride were added to the mixture in the reaction vessel. The temperature of the mixture in the reaction vessel was then raised to 70 C. Thereafter 63 grams (0.5 mole) of nonene (a propylene trimer) were added dropwise to the mixture in the reaction vessel over a period of about 40 minutes. During the addition of the noncne to the charge in .the reaction vessel the temperature of the reaction mixture was maintained between about 69 C. and 72 C. After the addition, the reaction mass was then held at about 70 C. for 15 minutes and the reaction was then complete. The excess phenol and boron triiluoride were then removed from the crude reaction mixture by fractional distillation at a reduced pressure ranging from about 22 mm. to about 24 mm. of mercury and a temperature ranging from about 71 C. to about 124 C. 106.6 grams of alkyl phenol, which was essentially nonyl phenol, remained as a residue. This residue was a colorless liquid having a Gardner color of 0.5.

A control was run as above, however, the presence of hypophosphorous during the alkylation of the phenol was omitted. The residue obtained in the control Was dark amber in color and had a Gardner color of 4.5.

Colors for the above example were determined by comparison against the Gardner 195.) standards. A Gardner color of zero represents a colorless liquid (distilled Water) and a Gardner color of 8 represents a very dark colored liquid.

Thus it is readily apparent that the color of an alkyl phenol can be greatly improved by the addition of hypophosphorous acid to the alkylation system.

Having described our invention what we claim as new and desire to secure by Letters Patent is:

1. In a process of reacting phenol with an alkylating agent in the presence of an alkylation catalyst to obtain alkyl phenols of improved color, the steps comprising mixing together phenol, alkylation catalyst and from about 0.05% to about 2.00% by weight, based on the total weight of said phenol and said alkylating agent, of at least one color inhibiting agent selected from the group consisting of hypophosphorous acid, sodium hypophosphite and calcium hypophosphite, introducing said alkylating agent to the resulting mixture, reacting said phenol and said alkylating agent and thereafter recovering a substantially color free alkyl phenol.

2. The process of claim 1, wherein said color inhibiting agent is hypophosphorous acid.

3. The process of claim 1, wherein said color inhibiting agent is sodium hypophosphite.

4. The process of claim 1, wherein said alkylating agent is at least one member of the group consisting of olefins having from 2 to 20 carbon atoms and alkyl halides having from 2 to 20 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,516,980 Gray et al Aug. 1, 1950 2,727,928 Menn et al Dec. 20, 1955 2,876,174 lreston May 3, 1959 

1. IN A PROCESS OF REACTING PHENOL WITH AN ALKYLATING AGENT IN THE PRESENCE OF AN ALKYLATION CATALYST TO OBTAIN ALKYL PHENOLS OF IMPROVED COLOR, THE STEPS COMPRISING MIXING TOGETHER PHENOL, ALKYLATION CATALYST AND FROM ABOUT 0.05% TO ABOUT 2.00% BY WEIGHT, BASED ON THE TOTAL WEIGHT OF SAID PHENOL AND SAID ALKYLATING AGENT, OF AT LEAST ONE COLOR INHIBITING AGENT SELECTED FROM THE GROUP CONSISTING OF HYPOPHOSPHOROUS ACID, SODIUM HYPOPHOSPHITE AND CALCIUM HYPOPHOSPHITE, INTRODUCING SAID ALKYLATING AGENT TO THE RESULTING MIXTURE, REACTING SAID PHENOL AND SAID ALKYLATING AGENT AND THEREAFTER RECOVERING A SUBSTANTIALLY COLOR-FREE ALKYL PHENOL. 